02 Pre Tensioning

Modeling of steel elements in civil engineering structures

Code_Aster, Salome-Meca course material GNU FDL licence (http://www.gnu.org/copyleft/fdl.html)

Outline Modeling of pre-tensioning Modeling of reinforcing steel

2 - Code_Aster and Salome-Meca course material

GNU FDL Licence

Modeling of pre-tensioning : principles Cable = bar elements embedded in a 3D or DKT mesh Mesh of bars independent of the concrete mesh


GNU FDL Licence

Modeling of pre-tensioning : principles The DEFI_CABLE_BP command creates loads corresponding to : The link (assumed perfect) between the cable and concrete : automatic definition of Lagrange multipliers The calculation of tension in the cables as recommended by BPEL (ETCC implementation in progress).

CAB1 = DEFI_CABLE_BP (...) CMCABbi=AFFE_CHAR_MECA( MODELE=MO, RELA_CINE_BP=_F(CABLE_BP=CAB_BPi, SIGM_BPEL=‘OUI' or 'NON', RELA_CINE='OUI' or 'NON'))


GNU FDL Licence

Modeling of pre-tensioning : DEFI_CABLE_BP command cabl_pr = DEFI_CABLE_BP ( ♦ MODELE = modele, ♦ CHAM_MATER = chmat, Required for calculating the tension ♦ CARA_ELEM = caelem, ♦ GROUP_MA_BETON = grmabe, Required for kinematic links ♦ DEFI_CABLE = _F ( ♦ GROUP_MA = grmaca, ♦ GROUP_NO_ANCRAGE = l_gnoa,) ♦ TYPE_ANCRAGE = (‘ACTIF’, ‘PASSIF’), ♦ TENSION_INIT = f0, Defining a ♦ RECUL_ANCRAGE = delta, cable ◊ RELAXATION = _F (♦ R_J = rj, ) ◊ CONE = _F ( ♦ RAYON = rayon, ♦ LONGUEUR = long, ♦ PRESENT = ('OUI','NON')) ◊ TITRE = l_titr, [l_tx]


GNU FDL Licence

Modeling of pre-tensioning : DEFI_CABLE_BP command cabl_pr

= DEFI_CABLE_BP (

♦ MODELE = modele, ♦ CHAM_MATER = chmat, ♦ CARA_ELEM = caelem,

GRI

N1

N2

N3

N4

N5

♦ GROUP_MA_BETON = grmabe,

♦ DEFI_CABLE = _F ( ♦ GROUP_MA = 'cable1',

cable1

♦ GROUP_NO_ANCRAGE = ('GRI','GRF',) ♦ TYPE_ANCRAGE = (‘ACTIF’, ‘PASSIF’), ♦ TENSION_INIT = f0, ♦ RECUL_ANCRAGE = delta, ◊ RELAXATION = _F (♦ R_J = rj, ) ◊ CONE = _F ( ♦ RAYON = rayon, ♦ LONGUEUR = long, ♦ PRESENT = ('OUI','NON'))

◊

TITRE = l_titr, [l_tx]


GNU FDL Licence

GRF

N6

Modeling of pre-tensioning : potential difficulties [U4.42.04]


GNU FDL Licence

Modeling of pre-tensioning : diffusion cone Possibility of introducing a diffusion cone Real situation

Without modelling the shaft

[U4.42.04]

With modeling of the effect of shaft vanishing

mesh size required management of redundant boundary conditions 8 - Code_Aster and Salome-Meca course material

GNU FDL Licence

Modeling of pre-tensioning : DEFI_CABLE_BP command cabl_pr

= DEFI_CABLE_BP (

♦ MODELE = modele, ♦ CHAM_MATER = chmat, ♦ CARA_ELEM = caelem, ♦ GROUP_MA_BETON = grmabe,

♦ DEFI_CABLE = _F ( ♦ GROUP_MA = 'cable1', ♦ GROUP_NO_ANCRAGE = ('GRI','GRF',) ♦ TYPE_ANCRAGE = (‘ACTIF’, ‘PASSIF’), ♦ TENSION_INIT = f0, ♦ RECUL_ANCRAGE = delta, ◊ RELAXATION = _F (♦ R_J = rj, )

Calculation of the tension

◊ CONE = _F (♦ RAYON = rayon, ♦ LONGUEUR = long, ♦ PRESENT = ('OUI','NON')) ◊

TITRE = l_titr, [l_tx]


GNU FDL Licence

Modeling of pre-tensioning : calculating the tension in the cables Calculating the tension at any point of the cable as recommended by BPEL91

[

5 F̃ ( s) ̃ F (s)= F (s){x flu ×F 0+ x ret × F 0 +r ( j)× ×ρ1000 100 S a× f

]

µ0 × F̃ ( s)} prg

Taking into account the instant losses by friction and anchor recoil

F c (s)= F 0 exp ( f αϕ s )

F c (s)× F̃ (s)=[ F c (d ) ]


2

GNU FDL Licence

Modeling of pre-tensioning : calculating the tension in the cables Calculating the tension at any point of the cable as recommended by BPEL91

[

]

5 F̃ ( s) ̃ F (s)= F (s){x flu ×F 0+ x ret × F 0 +r ( j )× µ0 × F̃ (s)} ×ρ1000 100 S a ×σ y Creep of concrete

Shrinkage of concrete

Relaxation of steel

Taking account of losses depending on time


GNU FDL Licence

Modeling of pre-tensioning : calculating the tension in the cables Data setting MBETON=DEFI_MATERIAU(ELAS=_F(E= 30.E9,...), BPEL_BETON= _F(

◊ PERT_FLUA = 0, ◊ PERT_RETR = 0),);

MCABLE=DEFI_MATERIAU( BPEL_ACIER=_F(

F 0, ∆ , r ( j )

Sa

ELAS=_F(E=200.E9 ), ◊FROT_COURB

=3.0E-3,

◊FROT_LINE

=1.5E-3,

◊F_PRG

=1.94E11,

◊RELAX_1000

= 0,

◊MU0_RELAX

= 0),)

in DEFI_CABLE_BP in AFFE_CARA_ELEM


GNU FDL Licence

Modeling of pre-tensioning : two strategies Tensions le long du câble 6,E+06

5,E+06

Tension (N)

4,E+06

3,E+06

2,E+06

1,E+06

0,E+00 1

11

21

31

41

51

61

71

81

91

101

111

121

131 Elément

BPEL

Solving with STAT_NON_LINE, instant tensioning Loss of tension due to the instant deformation of the concrete No possible phasing


GNU FDL Licence

DCBP sans correction

DCBP après correction

Command CALC_PRECONT Final tension in the cables = BPEL Allows successive tensioning in cables

Modeling of pre-tensioning : two strategies Strategy #1 chcab=AFFE_CHAR_MECA(... RELA_CINE_BP=_F( CABLE_BP=cable, SIGM_BPEL=‘OUI', RELA_CINE='OUI')) RES1 = STAT_NON_LINE(... EXCIT=(_F(CHARGE = CLIM,), _F(CHARGE = chcab)), ...,)


Strategy #2 chcab =AFFE_CHAR_MECA(... RELA_CINE_BP=_F( CABLE_BP=cable, SIGM_BPEL=‘NON', RELA_CINE='OUI',),); RES1 = CALC_PRECONT(... EXCIT=(_F(CHARGE =CLIM,), _F( CHARGE = chcab)), CABLE_BP=cable, ...,)

GNU FDL Licence

Modeling of pre-tensioning : two strategies Tensions le long du câble 6,E+06

Strategy #2 :

CALC_PRECONT

5,E+06

Tension (N)

4,E+06

Strategy #1 : 3,E+06

STAT_NON_LINE

2,E+06

1,E+06

0,E+00 1

11

21

31

41

51

61

71

81

91

101

111

121

131 Elément

BPEL

DCBP sans correction

DCBP après correction

STAT_NON_LINE

CALC_PRECONT

Instant tensioning Loss of tension due to the instant deformation of the concrete No possible phasing Easier implementation 15 - Code_Aster and Salome-Meca course material

Progressive tensioning Final tension in cables = BPEL Allows successive tensioning in cables A little more complex GNU FDL Licence

Modeling of pre-tensioning : tips for strategy #1 Combine a maximum cables in DEFI_CABLE_BP Option CONE : Pay attention to redundant connections (not factorable matrix) + size of elements If TYPE_ANCRAGE = ('PASSIF', 'PASSIF'), there is no tension in the cable ! In case of a continuation calculation (POURSUITE), define a new load without tension, otherwise the two tensions will be added chcab2=AFFE_CHAR_MECA(MODELE=MO, RELA_CINE_BP=_F(CABLE_BP=CAB_BPi, SIGM_BPEL=‘NON', RELA_CINE='OUI',),); RES1 = STAT_NON_LINE(reuse =RES1, ETAT_INIT=_F(EVOL_NOLI=RES1, EXCIT =(_F(CHARGE = CLIM,), _F(CHARGE = Chcab2), … ),) 16 - Code_Aster and Salome-Meca course material

GNU FDL Licence

Modeling of pre-tensioning : DEFI_CABLE_BP command statnl [evol_noli] = CALC_PRECONT( ◊ reuse = statnl, ◊ ETAT_INIT = _F(…)

Boundary conditions, instant loads, kinematic links related to cables already strained

♦ MODELE = mo , ♦ CHAM_MATER = chmat , ♦ CARA_ELEM = carac , ♦ COMP_INCR = _F()

♦ INCREMENT =_F(

♦ LIST_INST = litps , ◊ INST_FIN = instfin,),

♦ EXCIT =(_F( ♦ CHARGE = chi ), ), ♦ CABLE_BP = cabl_pr ,

The cables that will be strained between instini and instfin

◊ CABLE_BP_INACTIF = cabl_pr , Inactive cables (no stiffness) + mot-clé facteur STAT_NON_LINE)


GNU FDL Licence

Modeling of pre-tensioning : DEFI_CABLE_BP command, example CAB_BP=DEFI_CABLE_BP(...) CH_L=AFFE_CHAR_MECA(MODELE=MO, RELA_CINE_BP=_F(CABLE_BP=CAB_BP, SIGM_BPEL=‘NON', RELA_CINE='OUI',),);

EVOL = CALC_PRECONT(CABLE_BP = CAB_BP, EXCIT = _F(CHARGE = CL), INCREMENT =_F(LIST_INST=L, INST_FIN = 1., …) EVOL = STAT_NON_LINE(reuse =EVOL, ETAT_INIT =_F(EVOL_NOLI= EVOL) EXCIT=(_F(CHARGE= CL), F(CHARGE=CH_L),


GNU FDL Licence

1. definition of cables 2. CH_L contains the kinematic links

Modeling of pre-tensioning : DEFI_CABLE_BP command, example CAB_BP=DEFI_CABLE_BP(...) CH_L=AFFE_CHAR_MECA(MODELE=MO,

RELA_CINE_BP=_F(CABLE_BP=CAB_BPi,

SIGM_BPEL=‘NON', RELA_CINE='OUI',),);

EVOL = CALC_PRECONT(CABLE_BP = CAB_BP, EXCIT = _F(CHARGE = CL), INCREMENT =_F(LIST_INST=L, INST_FIN = 1., …) Tensioning of cables defined in CAB_BP, from t= 0 to 1 EVOL = STAT_NON_LINE(reuse =EVOL, ETAT_INIT =_F(EVOL_NOLI= EVOL) EXCIT=(_F(CHARGE= CL), F(CHARGE=CH_L), ….


GNU FDL Licence

Loads : only boundary conditions + instant loads

Modeling of pre-tensioning : DEFI_CABLE_BP command, example CAB_BP=DEFI_CABLE_BP(...) CH_L=AFFE_CHAR_MECA(MODELE=MO,

RELA_CINE_BP=_F(CABLE_BP=CAB_BPi,

SIGM_BPEL=‘NON', RELA_CINE='OUI',),); EVOL = CALC_PRECONT(CABLE_BP = CAB_BP, EXCIT = _F(CHARGE = CL), INCREMENT =_F(LIST_INST=L, INST_FIN = 1., …)

EVOL = STAT_NON_LINE(reuse =EVOL, ETAT_INIT =_F(EVOL_NOLI= EVOL) EXCIT=(_F(CHARGE= CL), F(CHARGE=CH_L), …. Continuation of the calculation Load : boundary conditions + kinematic links related to cables + other loads


GNU FDL Licence

Modeling of pre-tensioning : staging For staging, possibility of alternate or link STAT_NON_LINE and CALC_PRECONT Pay attention to the loads to be taken into account !

See documentation U2.03.06 or practical sessions


GNU FDL Licence

Modeling of staging Simulation suggested : BARRE element + DEFI_CABLE_BP + STAT_NON_LINE or CALC_PRECONT

But always possible to use temperature differentials, imposed deformation, ...


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Outline Modeling of pre-tensioning Modeling of reinforcing steel


GNU FDL Licence

Modeling of reinforcing steel In a 3D model Option #1 : use the BARRE model (or if needed POUTRE) Mesh steels with SEG2 elements Steel and concrete nodes must be identical

Option #2 : use the GRILLE_MEMBRANE model Steel is meshed with 2D elements : QUAD4, TRIA3, QUAD8, TRIA6 Overlay meshes for different directions of reinforcement (CREA_MAILLAGE) CREA_MAILLAGE( MODELE=MO, CREA_GROUP_MA=_F(NOM = 'barreH', GROUP_MA = 'surf', PREF_MAILLE='h')) 24 - Code_Aster and Salome-Meca course material

GNU FDL Licence

Modeling of reinforcing steel With a shell model (DKT) Use GRILLE_EXCENTREE The steel is meshed with linear 2D elements : QUAD4 or TRIA3 Overlay meshes for different directions of reinforcement (CREA_MAILLAGE)

For a 1D model Use of multi-fiber beam POU_D_EM


GNU FDL Licence

Modeling of reinforcing steel Model GRILLE_MEMBRANE Kinematics of the surface : no unknown for rotation Membrane elements without torsional stiffness Only one direction of reinforcement No possibility of eccentricity

Model GRILLE_EXCENTREE DKT shell kinematics: unknown for rotation Only one direction of reinforcement Opportunity to offset the grid


GNU FDL Licence

Modeling of reinforcing steel Possibility to explicitly represent the steels : With 1D elements With 2D elements, of membrane type (for isoparametric modeling) or DGT type (for plate modeling) Possibility of using global modeling of reinforced concrete : DKTG elements and GLRC-DM or GLRC-DAMA constitutive laws


GNU FDL Licence

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02 Pre Tensioning

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